<?php

// +----------------------------------------------------------------------

// | ThinkPHP [ WE CAN DO IT JUST THINK IT ]

// +----------------------------------------------------------------------

// | Copyright (c) 2009 http://thinkphp.cn All rights reserved.

// +----------------------------------------------------------------------

// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )

// +----------------------------------------------------------------------

// | Author: liu21st <liu21st@gmail.com>

// +----------------------------------------------------------------------

namespace Think\Crypt\Driver;

/**

 * Xxtea 加密实现类

 */

class Xxtea {



    /**

     * 加密字符串

     * @param string $str 字符串

     * @param string $key 加密key

     * @param integer $expire 有效期（秒）     

     * @return string

     */

    public static function encrypt($str, $key,$expire=0) {

        $expire = sprintf('%010d', $expire ? $expire + time():0);

        $str    =   $expire.$str;

        $v = self::str2long($str, true);

        $k = self::str2long($key, false);

        $n = count($v) - 1;



        $z = $v[$n];

        $y = $v[0];

        $delta = 0x9E3779B9;

        $q = floor(6 + 52 / ($n + 1));

        $sum = 0;

        while (0 < $q--) {

            $sum = self::int32($sum + $delta);

            $e = $sum >> 2 & 3;

            for ($p = 0; $p < $n; $p++) {

                $y = $v[$p + 1];

                $mx = self::int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self::int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));

                $z = $v[$p] = self::int32($v[$p] + $mx);

            }

            $y = $v[0];

            $mx = self::int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self::int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));

            $z = $v[$n] = self::int32($v[$n] + $mx);

        }

        return self::long2str($v, false);

    }



    /**

     * 解密字符串

     * @param string $str 字符串

     * @param string $key 加密key

     * @return string

     */

    public static function decrypt($str, $key) {

        $v = self::str2long($str, false);

        $k = self::str2long($key, false);

        $n = count($v) - 1;



        $z = $v[$n];

        $y = $v[0];

        $delta = 0x9E3779B9;

        $q = floor(6 + 52 / ($n + 1));

        $sum = self::int32($q * $delta);

        while ($sum != 0) {

            $e = $sum >> 2 & 3;

            for ($p = $n; $p > 0; $p--) {

                $z = $v[$p - 1];

                $mx = self::int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self::int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));

                $y = $v[$p] = self::int32($v[$p] - $mx);

            }

            $z = $v[$n];

            $mx = self::int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self::int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));

            $y = $v[0] = self::int32($v[0] - $mx);

            $sum = self::int32($sum - $delta);

        }

        $data   = self::long2str($v, true);

        $expire = substr($data,0,10);

        if($expire > 0 && $expire < time()) {

            return '';

        }

        $data   = substr($data,10);

        return $data;

    }



    private static function long2str($v, $w) {

        $len = count($v);

        $s = array();

        for ($i = 0; $i < $len; $i++) {

            $s[$i] = pack("V", $v[$i]);

        }

        if ($w) {

            return substr(join('', $s), 0, $v[$len - 1]);

        }else{

            return join('', $s);

        }

    }



    private static function str2long($s, $w) {

        $v = unpack("V*", $s. str_repeat("\0", (4 - strlen($s) % 4) & 3));

        $v = array_values($v);

        if ($w) {

            $v[count($v)] = strlen($s);

        }

        return $v;

    }



    private static function int32($n) {

        while ($n >= 2147483648) $n -= 4294967296;

        while ($n <= -2147483649) $n += 4294967296;

        return (int)$n;

    }



}